The present invention relates to an organic (electro-)luminescence device and particularly to an organic luminescence device for emitting light by applying an electric field to a film of an organic compound (organic compound layer).
An organic luminescence device generally comprises a pair of electrodes (comprising an anode and a cathode) and a film comprising a fluorescent organic compound disposed between the electrodes. Into the organic compound layer (film), holes and electrons are injected from the anode and the cathode, respectively, thus forming excitons of the fluorescent organic compound. When the excitons are returned to ground state, the organic luminescence device emits light or causes luminescence.
According to a study by Eastman Kodak Co. (xe2x80x9cAppl. Phys. Lett.xe2x80x9d, vol. 51, pp. 913- (1987)), it has been reported that a function-separation type organic luminescence layer comprising mutually laminated two layers including a layer of an aluminum quinolinol complex (as an electron transporting and luminescent material) and a layer of a triphenylamine derivative (as a hole transporting material) causes luminescence at a luminance (brightness) of ca. 1,000 cd/m2 under application of a voltage of ca. 10 volts. This is also reported in, e.g., U.S. Pat. Nos. 4,539,507; 4,720,432 and 4,885,211.
Further, by changing species of the fluorescent organic compound, it is possible to effect luminescence over broad wavelength regions ranging from an ultraviolet region to an infrared region. In this regard, various compounds have been extensively studied in recent years. Such compounds have been proposed in, e.g., U.S. Pat. Nos. 5,151,629, 5,409,783 and 5,382,477, and Japanese Laid-Open Patent Applications (JP-A) 2-247278, JP-A 3-255190, JP-A 5-202356, JP-A 9-202878 and JP-A 9-227576.
In addition to the above-mentioned organic luminescence devices using low-molecular weight materials, an organic luminescence device using a conjugated polymer has been reported by a research group of Cambridge University (xe2x80x9cNaturexe2x80x9d, vol. 347, pp. 539- (1990)). According to this report, a signal layer of polyphenylenevinylene (PPV) is formed through a wet-coating process and luminescence from the single layer is confirmed. Such an organic luminescence device using a conjugated polymer has also been proposed by, e.g., U.S. Pat. Nos. 5,247,190, 5,514,878 and 5,672,678, JP-A 4-145192, and JP-A 5-247460.
As described above, recent progress in organic luminescence device is noticeable, and the resultant organic luminescence devices are characterized by high luminance (brightness) under application of a low voltage, various (light-)emission wavelengths, high-speed responsiveness, small thickness and light weight, thus suggesting possibility of wide applications.
However, the above-described organic luminescence devices are still required to effect light output (emission) at a higher luminance and/or a higher conversion efficiency in the present state. These organic luminescence devices are also still insufficient in terms of durability such that the devices are liable to be changed in their properties with time when used for a long period or liable to be deteriorated by the influence of ambient air containing oxygen or of humidity. Further, in the case of using the organic luminescence devices for full-color display, it is necessary to effect luminescences of blue, green and red with good color purities. However, a satisfactory solution to the problem has not been realized yet, and particularly a red luminescence with a good color purity has not been satisfactorily provided.
On the other hand, spiro compounds having a unique three-dimensional structure and unique material properties have been noted as an organic functional material (J. Am. Chem. Soc. 110, p. 5687- (1988)). A proposal of using a Spiro compound in an organic luminescence device has been reported (JP-A 7-278537) but has failed to provide an electron-transporting layer or a luminescence layer exhibiting sufficient luminescence performance
A generic object of the present invention is to provide improvements to problems an mentioned above encountered in organic luminescence devices proposed heretofore.
A more specific object of the present invention is to provide an organic (electro-) luminescence device capable of effecting light output (emission) at high efficiency and luminance while realizing a prolonged life.
Another object of the present invention is to provide an organic luminescence device capable of providing a wide variety of emission wavelengths and emission hues, inclusive of particularly orange and red hues, and a good durability.
A further object of the present invention is to provide an organic luminescence device which can be produced easily and relatively inexpensively.
According to the present invention, there is provided an organic luminescence device, comprising: a pair of electrodes comprising an anode and a cathode, and a layer of organic compound disposed between the electrodes; wherein the organic compound layer contains at least one species of spiro compounds represented by formulae [I], [II] and [III] shown below: 
wherein R1, R2, R3 and R4 independently denote a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group or a nitro group;
Y denotes xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94,  greater than NR5 or xe2x80x94CHxe2x95x90CHxe2x80x94 wherein R5 denotes a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; and
X1 and X2 independently denote a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a nitro group, a substituted or unsubstituted amino group, or a group selected from those represented by structural formulae (IV)-(XIII) shown below with the proviso that at least one of X1 and X2 is selected from groups represented by the formulae (IV)-(XIII): 
wherein R6 to R14 independently denote a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, an alkoxyl group, or a nitro group;
Z1 and Z2 independently denote xe2x80x94Sxe2x80x94,  greater than NR15 or  greater than Si(R16)R17 wherein R15 denotes a hydrogen atom, an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group; R16 and R17 independently denote an alkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted heterocyclic group; and
L denotes an integer of 0-20, m denotes an integer of 0-20 with the proviso that L+m makes an integer of 1-20, and n is an integer of 1-20.
By using the spiro compound represented by the above-mentioned formula [I], [II] or [III] in the organic luminescence device, it becomes possible to effect luminescence at a very high luminance under application of a lower voltage and provide an excellent durability.
Particularly, the organic compound layer comprising the spiro compound of the formula [I], [II] or [III] used in the present invention is useful as an electron-transporting layer, and also as a luminscence layer.
Further, the organic compound layer can be prepared through vacuum deposition, casting, wet-coating, etc., thus readily realizing a larger size thereof relatively inexpensively.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawing.